Method for making an electric motor

ABSTRACT

Transverse flux electric motors are made using a unique process where individual components are premade and then assembled together. A stator portion is made by nesting a coil between two stator core portions. In a disclosed example, distinct first and second stator core portions are formed. The stator core portions in disclosed examples are made from laminations or sintered powder materials. In a disclosed arrangement, a coil is supported between the core portions of the stator such that the core portions enclose at least part of axial surfaces on the coil. A rotor that has a core and a plurality of magnets is supported relative to the stator for relative rotary motion such that the plurality of magnets of the rotor interact with the stator core portions during the relative rotary motion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/740,231 filed Dec. 18, 2000, now U.S. Pat. No. 6,552,068, issued Oct.4, 2005.

BACKGROUND OF THE INVENTION

This invention generally relates to transverse flux electric motors.More particularly, this invention relates to a strategy for fabricatingthe components of a transverse flux motor in a practical andcost-effective manner.

It has recently become apparent that there are significant advantages toutilizing gearless propulsion systems in elevator and escalator systems,for example. With a gearless propulsion arrangement, there are no geartrains between the propulsion machine or mechanism and the drivencomponents (such as the sheaves in an elevator system). Gearlesspropulsion systems typically have fewer components and are more compactthan traditional geared arrangements. An additional advantage is thatgearless propulsion systems reduce acoustic noise and simplifymaintenance procedures.

One challenge presented in attempting to use gearless propulsion systemsis that they typically require electric motors, which often provedifficult to make with the desired performance characteristics.Permanent magnet motors are advantageous because they are capable ofdeveloping higher torque densities with higher efficiency compared toinduction or switched reluctance arrangements. Permanent magnettransverse flux motors are capable of producing even higher torquedensities than permanent magnet brushless motors.

A significant challenge is presented when attempting to build such asystem because transverse flux machines are typically relativelyexpensive. The armature of a transverse flux motor has a complicatedstructure. Typical attempts include laminating arc-shaped sheets andembedding conductive coils in the laminated stack by arranging the coilswithin concentric slots. Although the process would be improved byutilizing wedge-shaped lamination sheets formed by a hot rollingprocess, that approach is undesirably expensive.

There is a need for an improved method of making the components oftransverse flux electric motors that avoids the complications andexpenses associated with current approaches. This invention addressesthose needs while avoiding the shortcomings and drawbacks of the priorart.

SUMMARY OF THE INVENTION

In general terms, this invention is a method for making transverse fluxmotor components. The method of this invention includes several basicsteps. A stator portion is made by forming first and second stator coreportions. A coil is supported between the core portions to complete thestator. A rotor is formed having a core and a plurality of magnets. Therotor and stator are then supported for relative rotary motion betweenthem such that the plurality of magnets of the rotor interact with thestator core portions during the relative rotary motion.

In a preferred embodiment, the stator includes support members on axialoutside surfaces of the core portions. The support members also maysupport a plurality of magnetic core members, which provide for enhancedflux transfer and motor performance.

An electric motor designed according to this invention includes a statorhaving first and second stator core portions and a coil supportedbetween the core portions. A rotor has a core and a plurality of magnetssupported on the core. The magnets preferably are permanent magnets. Thestator and rotor are supported for relative rotary motion between themsuch that the plurality of magnets of the rotor interact with the statorcore portions during relative rotary motion between them.

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following description ofthe currently preferred embodiments. The drawings that accompany thedetailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic, perspective illustration of an electric motorassembly designed according to this invention.

FIG. 2 is an exploded view of a stator designed according to thisinvention.

FIG. 3 illustrates the components of FIG. 2 in an assembled condition.

FIG. 4 is a partial cross-sectional view taken along the lines 4—4 inFIG. 2.

FIG. 5 is a perspective illustration of the stator during a laterportion of a preferred assembly process.

FIG. 6 illustrates another feature of a stator designed according tothis invention.

FIG. 7 is a diagrammatic, perspective illustration of a rotor designedaccording to this invention.

FIG. 8 is a perspective, diagrammatic illustration of another embodimentof a stator designed according to this invention.

FIG. 9 is a cross-sectional view of another embodiment of thisinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1–7 show a first example implementation of this invention. Anelectric motor assembly 20 includes a stator 22 and a rotor 24. Thestator 22 and rotor 24 are supported for relative rotary motion togenerate electrical power in a manner that is understood by thoseskilled in the art.

As best seen in FIGS. 2 and 3, the stator 22 preferably includes a coil26 supported between a pair of stator core portions 28. Each coreportion 28 preferably includes an inner coil supporting surface 30 and aplurality of radially extending projections 32. The stator poles areprovided by the projections 32, which preferably are equally,circumferentially spaced about the stator core portions 28 facing inwardtoward a central axis of the stator. The coil 26 preferably is placedbetween two opposing stator core portions 28 in a nesting relationshipas illustrated in FIG. 3.

In the illustrated example, although it is not required to achieve theresults provided by this invention, the projections 32 on the coreportions 28 preferably includes an axial outward surface 34 that extendsbeyond an axial outward surface 36 on the ring portion of each core 28.This is best seen in the illustration of FIG. 4. When the axiallyoutward surfaces 34 extend as illustrated, this provides a convenientmeans for placing outer support members 40 on each side of the stator22.

As best seen in FIG. 5, two outer support members 40 preferably arereceived about the outer axial surfaces of the core portions 28. Theouter support members 40 preferably include a plurality of slots 42 thatcorresponds to the number of projections 32 on the core portions 28. Theouter surfaces 34 on the projections 32 preferably are aligned with theoutermost surface of the support members 40 to provide a smooth outersurface.

In the preferred embodiment, the outer support members 40 include aplurality of receiver portions 44 that receive magnetic core members 46(shown in FIG. 6). The magnetic core portions 46 are provided in someexamples to increase the magnetic flux density across the air gapbetween the stator and rotor to achieve different flux densities fordifferent power levels, for example. The magnetic core members 46preferably have a [generally I-shaped] selected configuration so thatthey are snugly received between the two support members 40 and held inplace adjacent the coil 26. In one example, the core members 46 aregenerally I-shaped. In the illustrated example, the core members 46 havea generally T-shaped configuration. As illustrated, when magnetic coremembers 46 are utilized, they preferably are interspersed between thesets of projections 32 on the stator core portions 28.

It should be noted that the magnetic core portions 46 and the supportmembers 40 are not required in all embodiments of this invention. Thecurrently preferred embodiment of FIGS. 1–7 includes the support members40 and the core portions 46.

The various portions of the stator 22 preferably are individually madeand then assembled together in the general order shown as the figuresprogress in number. In other words, it is preferred to premake the coil26 and insert it between two premade stator core portions 28. Then theouter support members 40 can be assembled onto the outsides of the coreportions 28 and, if desired, the magnetic core portions 46 are theninserted in their positions.

The entire stator assembly preferably is coated using an epoxy resin,which ensures that the various components are held together. Otherbonding methods may be used to secure, for example, the two stator coreportions 28 together, which will maintain the coil 26 in a nestedposition between the core portions 28. The core portions 28 preferablyare made from sintered powder materials. Similarly, the core portions 46preferably are made from sintered powder materials. The outer supportportions 40 preferably are made from a non-ferromagnetic material. Theouter support portions 40 provide the ability to include magnetic coreportions 46, which magnify the magnetic flux density in the air gapbetween the stator 22 and the rotor 24.

As illustrated in FIG. 7, the rotor 24 preferably includes a rotor core50 and a plurality of permanent magnets 52. As is understood in the art,the permanent magnets 52, which are ring-shaped in the illustratedexample, include a plurality of north and south poles. The permanentmagnets 52 preferably are aligned on the core 50 such that when therotor 24 and stator 22 are in an assembled condition, the permanentmagnets 52 are positioned to interact with the projections 32 on thestator core portions 28 to generate electrical power as is known in theelectrical motor art.

Assembling individual components in the manner illustrated and discussedabove provides significant cost savings in manufacturing permanentmagnet transverse flux motors. When it is desired to have a multi-phasemotor, a plurality of stators 22 and rotors 24 can be stacked or alignedtogether and then supported in an appropriate housing (not illustrated).Given this description, those skilled in the art will understand how tosupport a plurality of such assemblies when desired.

In another example of this invention, sintered powder materials are notused for making the various components of the stator and rotor. Instead,laminations are preferred in some example implementations of thisinvention. One such example is illustrated in FIGS. 8 and 9 where a pairof radially laminated stacks 60 takes the place of the stator coreportions 28 of the previous example. In this example, the stator coreportions 60 are made from laminations instead of sintered powdermaterials. Because laminations are used, a separate yoke portion 62preferably is placed between the stator core portions 60 so that thecoil 26 may be supported between them in a nested fashion asillustrated. Forming laminations of the type illustrated including aring-shaped yoke 62 and the core portions 60 is possible and avoids thedifficulties of attempting to form laminations as required in previousdesigns. A variety of rotor core materials 50 may be used, includingsintered powders or laminations to support the permanent magnets 52. Theexample of FIGS. 8 and 9 operates the same as that in the previousfigures, it is just that different manufacturing processes and materialsare utilized.

This invention provides permanent magnet transverse flux motors that aremade using a unique process that is cost effective and more practicalthan previous attempts. The description provided gives exampleimplementations of this invention. The description is not to beinterpreted in a limiting sense. Variations and modifications may becomeapparent to those skilled in the art that do not necessarily depart fromthe purview and spirit of this invention. The scope of legal protectiongiven to this invention can only be determined by studying the followingclaims.

1. A method of making an electric motor, comprising the steps of: (A)forming a stator by (1) forming distinct first and second stator coreportions; (2) supporting a coil between the core portions such that thecore portions enclose at least part of axial surfaces on the coil; (B)forming a rotor having a core and a plurality of magnets; (C) supportingthe rotor relative to the stator for relative rotary motion between therotor and the stator such that the plurality of magnets of the rotorinteract with the stator core portions during relative rotary motionbetween the stator and the rotor.
 2. The method of claim 1, wherein step(A) includes supporting the core portions and the coil between twosupport members that enclose at least part of outward axial surfaces ofthe core portions.
 3. The method of claim 2, including supporting aplurality of magnetic core members by the support members.
 4. The methodof claim 3, including providing a plurality of slots on the supportmembers and inserting the magnetic core members in corresponding ones ofthe slots.
 5. The method of claim 1, wherein step (A) includes formingeach core portion such that each includes a generally annular ring and aplurality of circumferentially spaced projections that project radiallyinward from the ring.
 6. The method of claim 5, including providing twosupport members with a plurality of radially inwardly projecting spacerportions and interspersing the core portion projections and the spacerportions such that outward axial surfaces on the core projections arenot covered by the support members.
 7. The method of claim 6, includingforming a plurality of slots in the support members and inserting atleast one magnetic core member into each of at least some of the slots.8. The method of claim 1, including assembling a plurality of rotors anda corresponding plurality of stators to thereby form a multiphase motor.9. The method of claim 1, wherein step (A) includes applying a bondingagent to the stator after performing substeps (1) and (2).
 10. Themethod of claim 1, including forming the first and second stator coreportions using a sintered powder material.
 11. The method of claim 1,including forming the first and second stator core portions bylaminating a plurality of pieces to form a ring.